Ever since I was told that it is possible to tell 320kbps CBR from loseless, I've had some interest in hi-fi, and that was a few years ago. Today, I use an ASUS Xonar Essance sound card and an AKG Q701 headphone. I am pretty confident that it sounds better than all the cheaper alternatives I've had before, and I am quite proud of my own ability to eliminate biases without blind testing (because of lack of equipment). However, 320kbps MP3 is still transparent to me. The absolute best I can do is tell 128kbps, and it is extremely difficult as I have to go through the samples multiple times to try and spot one or two obvious distortions, and tell from that. If I couldn't find any than they sound identical to me. I have read through many of the FAQs, compilation of test results and older posts so I know this isn't uncommon and isn't what I am worried about. I keep everything loseless even though I can't tell the difference because I don't have that many music, only a few gigs which isn't a problem for today's mobile devices (exported selected few from CD images).

The biggest problem is I keep running into this claim that headphone amps are supposed to make ginormous differences, especially with the AKG Q701. Some people say there is more difference with the K701 but aren't they identical except the colors? Of course nobody could show any blind test results and they are nothing more than testimonies. I am not a hard core audiophile I don't have any audiophile friends so it's not possible so it is not possible for me to try out stand alone amps. It just seems to me that many of these audiophiles believe in some kind of mystical superiority of external boxes. You gotta have an external DAC, and an external amp and you have to connect them together. I mean today they are just intergraded circuits why do they have to be external? The Xonar Essance says "Headphone amp card" and it does have an amplifier chip as well as those small ones that you can swap out and everything, so What's the difference? In fact, I tried the Q701 on my cell phone, iPad, on-board intergraded audio, and even an iPod shuffle. They sound slightly worse I would say, the difference is quite subtle when compared to the Xonar. And I could not tell any difference between my phone, iPad and iPod shuffle.

I've also heard that you have to use an external power supply (it has a port that plugs into the computer power supply) for the Xonar to "bring out its full potential". Again, what's the difference? are computer power supplies not stabilized? I guess I also count as an overclocker so I know how voltages in the computer are set to two or three digits after the decimal, it is really sensitive stuff. I mean maybe the computer with its variable power requirement will destabilize the power source, but I don't listen to music while playing games or anything, I leave the computer idle for that. Also being a fairly high-end spec, the -12V power supply has a capacity of 650W (for 12V alone) , isn't that enough head room for small fluctuations?

The biggest problem is I keep running into this claim that headphone amps are supposed to make ginormous differences, especially with the AKG Q701. Some people say there is more difference with the K701 but aren't they identical except the colors? Of course nobody could show any blind test results and they are nothing more than testimonies. I am not a hard core audiophile I don't have any audiophile friends so it's not possible so it is not possible for me to try out stand alone amps. It just seems to me that many of these audiophiles believe in some kind of mystical superiority of external boxes.

Sometimes a headphone amp can make a difference. But, there is a TON on nonsense in the audiophile community and in audiophile marketing.

The parts to build a good headphone amp (or put one on a soundcard or motherboard) are not expensive. But, when you manufacture & distribute specialty items in small quanties, the costs go up. A nice cabinet also adds to the cost. So, an nice headphone amp could legitimately sell for a couple-hundred dollars, even if it doesn't sound any better than your average-good soundcard (or cheaper headphone amp). Plus, audiophiles are generally more-attracted to higher-price items.

Basically, there are 3 kinds of potential defects or differences in sound reproduction:Noise, distortion, and frequency response variations. So, if you read something like, "This amp has weak bass", or "This soundcard is noisy", that's engineering & scientific terminology and I'd tend to trust it. But, when someone says, "This headphone has more detail", I don't know what that really means, and I'm not sure anybody knows what it means in scientific terms or specifications.

If you are hearing noise in your headphones, you'll probably benefit from an external DAC & headphone amp (or from a better soundcard).

Otherwise, here's why a headphone amp can sometimes be an improvement:Impedance - Headphone impedance varies over the frequency spectrum, that's perfectly normal and acceptable and the impedance curve is different with every headphone. Bit if the souce impedance of your soundcard (or headphone amp) is high (say, close to the headphone impedance), the variations in headphone-impedance interact with the soundcard's impedance and you get variations in frequency response (not acceptable). I think it's usually a bump in the bass or mid-bass, but like I said every headpone is different. Technically, these frequency variations degrade the audio reproduction and it's not performing as designed or as specified. But, the frequency variations (such as an increase in bass) could actually heard as an improvement.

With high impedance headphones (i.e. 600 Ohms) this isn't an issue, and you won't get different frequency response from different soundcards or headphone amps (assuming no actual defects).

Most headphone amplifiers should have low impedance, so this shouldn't be an issue. It might not be an issue with most soundcards either, but a "line output" could be higher impedance.

What complicates this is that the output impedance specs are not always clear... The specs for the headphone amp might say "32 Ohms", but that's usually the (minimum) recomended headphone impedance, not the internal impedance of the headphone amp itself, which is hopefully much lower. (The goal is not to "match" the impedance. With headphone amps & power amps, the amp shoud have much lower internal output-impedance than the actual load.)

Voltage - If you are not getting enough volume without distortion, a headphone amp will generally help because they are usually designed for higher-voltage output than an average sooundcard.

Voltage is also related to impedance... A higher impedance headphone (i.e. 600 Ohm) requires more voltage to get the same power (milliwatts) and loudness as a lower impedance headphone.

QUOTE

I've also heard that you have to use an external power supply (it has a port that plugs into the computer power supply) for the Xonar to "bring out its full potential".

This could be a voltage issue. I don't remember if there is +/- 12V on the PCI bus. I would assume so because they used to have +/-12V RS-232 ports on I/O cards, but I don't know for sure.

That means I need to listen to a song and analyze the instruments/chord/arrangement etc and use MIDI instruments to reproduce the song. Some earphones can reveal the starting point (attack) of a note/chord more clearly so I can identify the correct pitch/chord easier. Some people may think that it is because different earphones have different frequency response but at least I can't imitate earphones' A's response on earphones B using EQ.

In fact there are transient-driven VST effects like Voxengo Transmodder and Waves TransX to enhance or reduce transient (not to confuse with a multiband dynamic processor).

EDIT: I didn't read the discussions thoroughly. I am talking about different earphones, not headphone amps. For headphone amps I have no opinions as I have never compare them carefully.

That means I need to listen to a song and analyze the instruments/chord/arrangement etc and use MIDI instruments to reproduce the song. Some earphones can reveal the starting point (attack) of a note/chord more clearly so I can identify the correct pitch/chord easier. Some people may think that it is because different earphones have different frequency response but at least I can't imitate earphones' A's response on earphones B using EQ.

In fact there are transient-driven VST effects like Voxengo Transmodder and Waves TransX to enhance or reduce transient (not to confuse with a multiband dynamic processor).

In basic system theory, impulse and step response are a way to characterize system behavior on time domain, but they are (roughly) the equivalent of frequency response on frequency domain. That's why a put a smiley on my reply: they basically give you the same (or comparable) informations, but could make some time related aspects more evident, like risetime, over/under-shots amplitude, time to zero error after a transient, which are related to signal tracking precision and thus qualitatively I think may be considered as "ability in revealing details".

That said, a pulse or a step contain frequencies that are completely out of audible range and nowhere to be found in musical signals, so it's completely normal to see an audio transducer smoothing and by a lot a square wave or changing a pulse in something resembling a sinc without drawing negative conclusions on sound quality aspects, if it has a flat frequency response in audio band.

Anyway, you can't exactly "imitate" two very differently built transducers (headphones or speakers), not without real feedback at least, just compensate for slightly different FR with EQ, which is a kind of feedforward action, within their respective physical limits of course.